Gas-filled display panels have been known for many years; examples of such panels are PANAPLEX panels and SELF-SCAN panels, both of which are made and sold by Burroughs Corporation. These panels are commercially successful, and they operate well, but they do not have memory; that is, a message or character cannot be introduced into these panels by the application of a signal and then retained after that signal has terminated. For a long time, a need has existed for a display panel having the simplicity and reliability of the PANAPLEX and SELF-SCAN panels and also having memory, because of the reliability and high brightness that such a panel would exhibit and the simplicity of its operating circuitry.
One type of prior art panel which has memory is illustrated in U.S. Pat. No. 3,559,190 of Bitzer et al. This panel is an A.C. panel; that is, it employs an A.C. signal applied to electrodes that are insulated from the gas in the panel. The Bitzer et al. panel has a single layer of cells in an internal cellular construction. Because of the isolation afforded by the cellular construction, the individual cells of the panel have a serious first electron problem, and many of the cells are consequently difficult to turn on. A modification of the Bitzer et al. panel is illustrated in U.S. Pat. No. 3,499,167 of Baker et al. as an open construction. While the Baker et al. panel solves the first electron problem, it has a problem with cell definition, and the electronic circuitry it requires is complex and expensive.
Another panel having memory and having considerable potential promise is described in U.S. Pat. No. 3,921,021 of Glaser et al. The present invention is an improvement over the Glaser et al. panel, involving a different mode of operation and a consequent simpler construction and operating circuitry.